Small capacitors across switches lengthen closures

Many switches carry a .05 or .047 uF non-polarized ceramic disc capacitor (16 V or more) that stretches the closure so the MPU can read it. These are often cut off or broken; replace them.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• Clear stuck switches using switch test
• Test a playfield switch diode
• What bad switch diodes do to the matrix
• A rollover button keeps scoring on its own: leaky capacitor across the switch
• MPU switch connector pins J2 and J3
• Some games add a sixth switch strobe ST5 (switches 41-48)
• Bally switch matrix: 5 strobes by 8 returns, numbered 1 to 40
• Prove the MPU switch inputs with the harness unplugged

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)